dental embry, histo, and anatomy ch 3-4 quiz

embryology

the study of prenatal development

prenatal development

• begins with the start of pregnancy and continues until the birth of the child

• 9 month gestation period divided into 3 trimesters

primordium

• the earliest indication of a tissue type or an organ during prenatal development

preimplantation period

• begins during first week after conception

• most congenital malformations (birth defects) occur during both the preimplantation and embryonic period

• a woman’s ovum is penetrated by sperm during fertilization and final stage of meiosis occurs in ovum

• zygote (fertilized egg) forms

  • undergoes mitosis to form cleavage

  • becomes morula

  • becomes vesicle known as blastocyst

  • end of first week blastocyst implants into endometrium

congenital malformations

• birth defects

• evident at birth

• most occur during both the preimplantation period and the embryonic period

amniocentesis

• amniotic fluid test (AFT)

• is a prenatal diagnostic procedure to detect chromosomal abnormalities where the amniotic fluid is removed and its fetal cells are grown for microscopic study of the chromosomes and sampled for other fetal complications

Non-invasive prenatal testing (NIPT)

• new type of prenatal genetic test that does not pose any risk

• a cell free fetal DNA testing that involves a simple blood draw from the pregnant women

teratogens

• environmental agents and factors that include infections, drugs, and radiation that are considered __

chemical teratogens

• methylmercury

• polychlorinated biphenyls

drug teratogens

• ethanol

• tetracycline

• phenytoin sodium

• lithium

• methotrexate

• aminopterin

• diethylstilbestrol

• warfarin

• thalidomide

• isotretinoin (retinoic acid)

• androgens

• progesterone

infectious teratogens

• rubella virus

• syphilis spirochete

• herpes simplex virus

• human immunodeficiency virus (HIV)

radiation teratogen

• high levels of ionizing radiation

• depends on the dose and severity

• can cause cleft lip or cleft palate

• may injure embryonic cells, resulting in cell death, chromosomal injurt, and delay of intellectual and physical growth

zygote

fertilized egg

meiosis

• joining of chromosomes from both biologic parents forms a new individual with “shuffled” chromosomes

• joining of sperm and ovum creates a diploid cell with 46 chromosomes (23 from dad, 23 from mom)

• this diploid cell goes through meiosis to shuffle genetic material and form 4 haploid daughter cells with 23 chromosomes

cleavage

• After implantation, the zygote undergoes mitosis (individual cell divison) that splits it into more and more cells

morula

• after initial cleavage

• the solid ball of cells

• gets its name for having the appearance of a mulberrry

blastocyst

• Due to the ongoing process of mitosis and secretion of fluid by the cells within the morula, the zygote becomes a vesicle known as a blastocyst

• also known as blastula

• travels down the fallopian tube then undergoes implantation in the endometrium lining of the uterus

trophoblast and embryoblast layers

• after a week of cleavage, the blastocysts consists of a layer of peripheral cells and a small inner mass of embryonic cells

trophoblast layer

• layer of peripheral cells located on the top of the blastocyst

• will give rise to important prenatal tissues

embryoblast layer

• layer of peripheral cells found as the inner cell mass of the blastocyst

• what will later become an embryo

syndrome

• a group of specific signs and symptoms

down syndrome

• also known as trisomy 21

• An extra chromosome number 21 is present after meiotic division

• characterized by epicanthic folds, oblique eyelid fissures, flat-bridged nose, furrowed lower lip, widely-spaced eyes, and a flat broad face

• increased levels of periodontal disease, delayed tooth eruption, fewer teeth present, microdontia, and increased risk of alzheimer’s disease

ectopic pregnancy

• when implantation may occur outside the uterus, involving the condition

• most occur within fallopian tube

• associated with factors that delay or prevent transport of the dividing zygote to the uterus

embryonic period

• the second period of prenatal development

• extends from the beginning of the second week to the twelfth week

induction

• developmental process

• action of one group of cells on another that leads to establishment of developmental pathway in responding tissue

• first step, planning stage

• signals are sent and cells communicate in order to guide what each part will develop into

proliferation

• controlled cellular growth and accumulation of byproducts

• massive cell growth to have enough “materials” for plans

• growth may be appositional or interstitial

differentiation

• change in identical embryonic cells to become distinct structurally and functionally

• cells become specialized to do unique jobs

• occurs at various rates

morphogenesis

• development of specific tissue structure or differing form due to embryonic cell migration or proliferation and inductive interactions

• development of specific tissue structure or shape

• body starts taking and forming physical shape

maturation

• final stage, finishing touch

• attainment of adult function and size due to proliferation, differentiation, morphogenesis

• cells and organs complete development and start working properly

appositional growth

• tissue enlarges its size by the addition of layers on the outside of a structure

interstitial growth

• occurs from deep within a tissue or organ

• inter = inside

cytodifferentiation

• is the development of different cell types

histodifferentiation

• is the development of different histologic tissue types within a structure

morphodifferentiation

• is the development of the differing morphology, which makes up its structure or shape, for each organ or system

second week of prenatal development

• implanted blastocyst grows

• Increased number of embryonic cells creates the embryonic cell layers (germ layers) within the blastocyst

• A bilaminar embryonic disc is eventually developed

• The disc is suspended in the endometrium lining the uterus between two fluid-filled cavities, the amniotic cavity and the yolk sac

• These layers are the ectoderm and endoderm

• The placenta develops from interactions of the trophoblast layer and the endometrial tissue

bilaminar embryonic disc

• developed from the blastocyst and appears as a three dimensional but flattened, essentially circular plate of bi layer cells

• consists of ectoderm (top layer)

• and endoderm (bottom layer)

ectoderm

• origin: epiblast layer

• histologic features: columnar

• future structures: epidermis; sensory epithelium of eyes, ears, nose, nervous system, neural crest cells; mammary and cutaneous glands

mesoderm

• origin: migrating cells from epiblast layer (primitive streak)

• Histologic features: varies

• future structures: dermis, muscle, bone, lymphatics, blood cells and bone marrow, cartilage, reproductive and excretory organs

endoderm

• origin: migrating cells from epiblast layer

• histologic features: cuboidal

• future structures: respiratory and digestive system linings, liver, pancreatic cells

neural crest cells

• origin: migrating neuroectoderm

• histologic features: varies

• future structures: components of nervous system pigment cells, connective tissue proper, cartilage, bone, certain dental tissue

• migrate from the crests of the neural folds and disperse within mesenchyme

• essential in formation of most oral and dental tissue except for the enamel and certain types of cementum as well as the development of the face and neck

placenta

• a prenatal organ that joins the pregnant female and the developing embryo

• develops from interactions of the trophoblast layer and endometrial tissue

• permit selective exchange of soluble bloodborne substances between them (O, CO2, and nutritional/ hormonal substances)

third week

• The primitive streak forms within the bilaminar embryonic disc

• primitive streak causes bilateral symmetry

• Cells from the primitive streak migrate and move down, eventually becoming the mesoderm, causing the bilaminar disc to be trilamniar

• cephalic end forms along with the oropharyngeal membrane

• oropharyngeal membrane includes ectoderm and endoderm but NO MESODERM

• This membrane is the location of the primitive mouth (stomodeum) of the embryo and the beginning of the digestive tract

• trilaminar disc also has a caudal end

• CNS begins to develop

• formation of the neuroectoderm from the ectoderm within the neural plate that thickens to form the neural groove

• neural groove deepens to become surrounded by the neural folds

• neural folds meet and fuse, forming the neural tube

• neural crest cells develop from neuroectoderm and migrate from the crests of neural folds and disperse within the mesenchyme

  • vital in the formation of most oral and dental tissue, except for the enamel and certain types of cementum, as well as the development of the face and neck

• By the end of the third week, the mesoderm differentiates and divides on each side of the neural tube to form somites

neural plate

• central band of cells that extends the length of the embryo from the cephalic end to caudal end

• undergoes further growth and thickening

neural groove

• after the neural plate undergoes further growth and thickening, it deepens and invaginates inward forming the __ __

neural folds

• near the end of the third week, the neural groove deepens further and is surrounded by the __ __

neural tube

• is formed during the fourth week by the neural folds undergoing fusion at the most superior part

somites

• 38-paired cuboidal segments of mesoderm

• located on both sides of the developing nervous system

fourth week

• disc undergoes embryonic folding as a result of extensive growth of ectoderm and there is development of the brain and spinal cord, heart, and digestive tract

• movement of embryonic cell layers form long and hollow tube lined by endoderm from oropharyngeal membrane to cloacal membrane

  • anterior part of this tube is the foregut

  • two posterior parts are midgut and hindgut

• face and neck begin to develop, with the primitive eyes, ears, nose, oral cavity, and jaw areas

foregut

• forms the primitive pharynx or primitive throat and includes a part of the primitive yolk sac as it becomes enclosed with folding

midgut

• forms the rest of the mature pharynx

hindgut

• behind (hiny)

• forms the remainder of digestive tract

ectodermal dysplasia

• abnormal development of one or more structures of ectoderm

• partial or incomplete anodontia of some or all teeth in each dentition

• teeth present frequently have developmental distubances

anodontia

• no

• absence of some or all teeth in each dentition

treacher collins syndrome (TCS)

• if there is a failure of migration of the neural crest cells to the facial region, TCS or mandibulofacial dysostosis develops in the embryo

• failure of specific orofacial development

  • downward slanting eyes

  • underdeveloped zygomatic bone

  • drooping lateral lower eyelids

  • Conductive hearing loss with malformed or absent ears

  • dental developmental disturbances such as adontia, enamel dysplasia with abnormal mineralization, and micrognathia

micrognathia

• small lower jaw

rubella

• an example of an infective teratogen

• results in cataracts, cardiac defects, and deafness

syphilis

• another infective teratogen

• bacterial spirochete causing treponema pallidum

• produces defects in incisors (hutchinson incisor) and molars (mulberry molar) as well as blindness, deafness, and possible paralysis if not treated

hutchinson incisor

• a dental anomaly associated with congenital syphilis.

• They are characterized by peg-shaped, notched, and widely spaced upper central incisors.

mulberry molar

• a dental anomaly associated with congenital syphilis.

• the permanent first molars have a characteristic rounded, bumpy surface, resembling a mulberry

fetal alcohol syndrome

• presents with noted orofacial features and various levels of intellectual disability

• cause by the pregnant woman’s excessive use of ethanol during the embryonic period

• characterized by

  • small midface

  • indistinct philtrum

  • thin upper lip

  • widely spaced eyes

  • epicanthic fold

  • low nasal bridge

  • short nose

spinal bifida

• failure of fusion of neural tube results in neural tube defects of the tissue overlying the spinal cord

• characterized by defects in vertebral arches and various degrees of disability

fetal period

• follows the embryonic period and begins from the twelfth week (third month) aka begins during the second trimester

• maturation of existing structures occurring as the embryo enlarges to become a fetus

• includes further proliferation, differentiation, and morphogenesis

tetracycline stain

• systemic tetracycline antibiotic therapy of the pregnant woman can act as a teratogenic drug during fetal period

• intrinsic yellow to yellow-brown discoloration within teeth can occur in slight, moderate, or severe degrees as antibiotic becomes chemically bound to tooth

• easily visible

• permanent teeth may be effected

• may require full cover crowns or veneers to improve appearance or even whitening

the face and its associated tissue begin to form during the __ week of prenatal development within the embryonic period

• fourth week

• the fourth to twelfth week are the most important for DHCP to know because most orofacial structures are formed

facial development within the fourth week of prenatal development

• disintegration of the oropharyngeal membrane of stomodeum enlarges primitive mouth, allowing access to the primitive pharynx and further growth

• mandibular processes fuse to form the mandibular arch that then fuses to form the mandible and lower lip

• frontonasal process forms and gives rise to the nasal placodes, nasal pits, medial and lateral nasal processes, and intermaxillary segment to form the nose and primary palate

  • intermaxillary segment forms four front teeth

• maxillary process forms from the mandibular arch on each side of the stomodeum

• maxillary processes fuse with each medial nasal process to form upper lip and with each mandibular arch to form the labial commissures

in the fourth week, organs begin to form developing stages in the embryo, this process is known as

• organogenesis

• brain, face, and heart are now noted as developing organs

embryonic layers involved in facial development

• all three embryonic layers are involved in facial development

  • this includes the ectoderm

  • the mesoderm

  • and the endoderm

early development of the face is due to ___ and __ of the ectomesenchhyme that is derived from neural crest cells

• proliferation and migration

how to facial structures become smooth?

• with most facial fusion, furrow are eliminated as underlying mesenchyme migrates into the furrow

• this migration takes place because adjacent mesenchyme grows and merges beneath external ectoderm during the maturation of the structure

also known as primitive mouth

• stomodeum

• is limited in depth by the oropharyngeal membrane which eventually disintegrates, allowing the cavity to connect to the developing digestive tract

mesenchyme

• a loosely organized, mainly mesodermal embryonic connective tissue which develops into connective and skeletal tissues, including blood and lymph

ectomesenchyme

• a type of mesenchyme derived from the neural crest, specifically in the cranial region during vertebrate development

• mesoderm taken over by neural crest cells

oropharyngeal membrane

• separates the stomodeum from the primitive pharynx

• the first event in development of the face during the latter part of the fourth week of prenatal development is disintegration of the oropharyngeal membrane

mandibular processes

• two bulges that appear inferior to primitive mouth

• consist of a core of mesenchyme formed in part by NCCs that migrated to the facial region

• fuse to form mandibular arch

developing mandibular arch

• gives rise to the lower face, the lower lip, mandibular teeth, and associated tissue

• After fusion of the left and right mandibular processes, the mandibular arch extends as a band of tissue inferior to the stomodeum and between the developing brain and heart

Meckel cartilage

• forms within each mandibular arch during growth

• most disappears as the bony mandible forms by intramembranous ossification lateral to and in close association with cartilage

frontonasal process

• begins to develop during the fourth week as a bulge of tissue at the most cephalic end of the embryo

• origin: ectodermal tissue and neural crest cells

• future structures: medial and lateral nasal processes

placodes

• rounded areas of specialized thickened ectoderm found at the location of developing special sense organs

• lens, otic, nasal

oronasal membrane

• originally separates stomodeum and nasal sacs

the face develops __ and __

• medially and inferiorly

• everything growing joins and meets at nasal (coming up and down, and from side to side to meet in the middle)

intermaxillary segment

• the paired medial nasal processes also fuse internally and grow inferiorly on the inside of the stomodeum, forming the __ ___ by the end of seventh week

upper and lower lip formation

• the maxillary processes contribute to the sides of the upper lip and the two medial nasal process contribute to the midline philtrum

cleft lip

• results from failure of fusion of the maxillary process with the medial nasal process

• varying degrees of disfigurement

branchial apparatus or pharyngeal apparatus

• consists of the arches, grooves, and membranes, as well as pouches

• Arches are made from mesoderm

• clefts formed from ectoderm

• pouch formed from endoderm

first pharyngeal arch

• mandibular arch

• contain meckel cartilage

• everything we need to chew

  • forms the trigeminal nerve

  • maxilla

  • mandible

  • incus

  • malleus

  • temporal bone

  • zygomatic bone

  • muscles of mastication (temporalis, pterygoid, masseter)

the neck develops from the primitive __ and the __apparatus

• primitive pharynx

• the brachial (pharyngeal) apparatus

the pharyngeal apparatus consists of arches, __ ,membranes, and __

• grooves

• pouches

second pharyngeal arch

• known as the hyoid arch

• consists of cartilage similar to first pharyngeal arch call Reichert cartilage

• forming facial expressions

  • forms the facial nerve

  • styloid process

  • hyoid bone

  • stapes

  • posterior belly of the digastric muscle

  • stylohyoid

  • stapedius

third pharyngeal arch

• helps swallow

• unnamed cartilage

  • forms glossopharyngeal nerve

  • forms stylopharyngeus

fourth and sixth pharyngeal arch

• laryngeal cartilages

  • forms the vagus nerve

  • does not form bones

  • forms superior and recurrent laryngeal nerves

a condition that may occur if the second pharyngeal groove does not obliterate is a __ cyst

• brachial cleft cyst

failure of fusion processes can result in__ lip or _ palate

• cleft lip or cleft palate